The add-on developers probably only have themselves to blame; they are almost always advised on major changes to an app well in advance of the official release and its up to them to make the necessary adjustments. I haven't heard any credible reports from credible sources that Firefox just went ahead and sprung this new version 'out of the blue', without warning, so it can be presumed the add-on developers did indeed get warnings; it may be those developers who decided not to revise their add-ons did so because they either no longer wished to spend more time on the add-ons, were incapable of making the necessary revisions, or decided not to support Firefox users in favor of the users of Chrome, Edge, etc. In some cases, Firefox really might not be to blame...
An alternative view of Firefox Quantum from
Wired:
Ciao, Chrome: Firefox Quantum Is The Browser Built for 2017 --
https://www.wired.com/story/firefox-...uilt-for-2017/
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